Polyphase generator windings

ABSTRACT

Each phase of a polyphase armature winding is constituted by a pair of phase belts, each belt consisting of three segments of the winding. The first and third segments in each belt are connected in series with one another and the remaining segment is series-connected with a corresponding segment of the opposite phase belt. Each phase is thus constituted by three separate circuits, but only a single connection ring per phase is necessary to connect segments laying on opposite sides of the armature.

United States Patent Willyoung 1 1 May 2, 197 2 s41 POLYPHASE GENERATORWINDINGS 3,201,627 8/1965 Harrington ..310/198 1121 1mm MM-WmywnwwiaN-Y-31233125; 341323 ilfiifffii: .iiiiifiiifii [73] Assignee: GeneralElectric Company Primary Examiner-J. D. Miller [22] Med: 1970 AssistantExaminer-R. Skudy [21] APpL 31,496 Attorney-William C. Crutcher, FrankL. Neuhau'ser, Oscar B.

Waddell and Joseph B. Forman [52] U.S. Cl. ..3l0/l98, 310/205 [57BSTRACT [51] Int. Cl. ..H02k 3/00 58 Field oi Search ..310/198, 199,195,202, 203, Phase a WlYPhase by I 310/205 206 207 179 171 a pan ofphase belts, each belt cons1st1ng of three segments of the winding. Thefirst and third segments in each belt are con- 56] References Citednected in series with one another and the remaining segment isseries-connected with a corresponding segment of the op- UNITED STATESPATENTS posite phase belt. Each phase is thus constituted by threeseparate circuits, but only a single connection ring per phase is2,015,562 9/ l 935 Kllgore ..3 10/202 necessary to connect Segment-Slaying on opposite Sides of the 2,778,962 l/l957 Taylor ...3 10/202armature. 2,778,963 l/l957 Habermann ...310/202 I 3,152,273 10/1964Harrington ..3 lO/198 3 Claim, 6 Drawing Figures Patented M5, 2, *19123,660,705

2 Sheets-Sheet 1 PHASE C PHASE A PHASE 8 INVENTORI DAVID M. WILLYOUNG,

HIS ATTORNEY.

Patented May 2, 1972 3,660,705

2 Sheets-Shoot 2 F|G.3 (PRIOR ART) F|G.4 (PRIOR ART) A 2 v q 3 INVENTORZDAVID M. WILLYOUNG,

BY MAL,

HIS ATTORNEY.

POLYPIIASE GENERATOR WINDINGS BACKGROUND OF THE INVENTION The presentinvention relates generally to the windings of polyphase dynamoelectricmachines, and more particularly to an improved armature connectionwherein each phase of the armature windings may consist of a pluralityof parallel circuits with a minimum of space required in the end turnregion for winding interconnections.

A polyphase generator may comprise a two-pole field element rotatablewithin a stationary cylindrical armature, or stator. The armature coreis formed of a suitable material such as is well known in the art and isprovided with a plurality of radial slots which are formed in and extendaxially along the inner surface of the stator core. The armaturewindings are each carried within appropriate ones of these slots, andmay be combined into a desired pattern or configuration so as to providemulti-phase electric power. Typically, three separate phases areprovided within the stator, and a two-pole field element is rotatedtherewithin at 3,600 rpm to produce threephase electric power at afrequency of 60 cycles per second.

In order to connect theaforementioned windings into the desiredconfiguration, connecting rings to provide appropriate connectionbetween individual winding segments are usually provided at one end ofthe stator, extending peripherally about the ends of the stator core.Since the windings are usually connected into groups consisting of aplurality of individual windings which are distributed about a portionof the inside diameter of the stator, many connections are necessary.Due to the limited space available between the inner and outer diametersof the stator core, the connections are usually constructed in layerswhich extend axially outward from the end of the stator. It will beappreciated that the more complex the connection configuration, the moreconnections will be necessary, thus utilizing additional material andcausing the overall length of the machine to increase. This not onlyincreases the size and Weight of the machine but requires a longer spanbetween support points for the rotor shaft, necessitating a largerdiameter and stronger shaft.

Many efforts have been made to obtain maximum power and efficiency froma polyphase generator of the type described above by modifying thestator winding circuit configuration. Two improvements in this field arethose disclosed in US. Pat. No. 2,778,963, granted on Jan. 22, 1957 toRudolph Habermann, Jr.; and in US. Pat. No. 3,l52,273, granted on Oct.6, I964 to D. B. Harrington, both of which are assigned to the assigneeof the present invention. In both of these patents it is taught thateach of the three phases of an armature winding may consist of threeparallel circuits, each of which comprises a pair of series-connectedsegments of the winding. According to the prior art, one segment of eachcircuit is located in one phase belt and the other segment, connected inseries therewith is located in another phase belt disposed atdiametrically opposed point within the stator.

The coils constituting various winding segments of the phase belts areinterleaved in a suitable sequence to minimize phase imbalance among thethree individual circuits. The sequence may be any of the severalarrangements taught by the prior art, although it has been foundadvantageous to use reversed, or mirror-image," sequence in oppositephase belts so that corresponding coils in series-connected segmentssimultaneously occupy nearly the same electrical position under rotorpoles of opposite polarity.

It has been the practice to series-connect diametrically oppositesegments i.e., those under opposite poles. This necessitates the use ofconnection rings to connect the segments in series. Because of thepresence of the rotor, such series connections must be routed about thecircumference of the stator through an arc of approximately I80". Sincethere are three phases and three circuits within each phase, there mustnecessarily be at least nine series connection rings within each machineso connected.

It is therefore an object of the present invention to provide apolyphase dynamoelectric machine each phase thereof comprising aplurality of parallel circuits, but requiring a reduced number ofconnection rings.

It is a further object of the present invention to provide adynamo-electric machine whose phases are each constituted by a pluralityof parallel circuits, the windings comprising at least some of whichcircuits are disposed entirely within a single phase belt.

SUMMARY OF THE INVENTION The subject invention contemplates the seriesconnection of pairs of winding segments which are distributed under acommon pole and have voltages of a common magnitude generated therein.Since there are in the disclosed embodiment three winding segmentsdistributed under any pole, the series connection of two of suchsegments leaves one segment unconnected. This leftover, or odd segmentis connected in series with the corresponding segment beneath theopposite rotor pole by means of a connection as is taught by the priorart.

By distributing first segments of pairs of winding segments in a firstsequence in a phase belt, and the second segments of said pairs in thereverse or mirror-image sequence in the same phase belt, the voltagesgenerated in said first and second segments will automatically beidentical in magnitude, although offset in phase angle from each otherand from the phase position of the vector sum resulting from theirseries connection, (which necessarily must fall at a phase anglecorresponding to the centerline position of said phase belt). Since thefirst and second segments utilize corresponding circuit positionssymmetrically disposed about the centerline of the phase belt, theremaining circuit positions which the third segment must occupy areautomatically equally disposed about the phase belt centerline, so thatthe phase angle of the generated voltage in the third segmentcorresponds to that of the centerline of the phase belt, and that of thevector sum of said first and second phase belt segments.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, both as to itsorganization and principle of operation, together with further objectand advantages thereof, will best be understood with reference to thefollowing specification taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a schematic illustration of a portion of a polyphasedynamoelectric machine showing the stator coils comprising one phase ofthe armature winding thereof;

FIG. 2 is a combined schematic diagram of the phase belt arrangement inan armature winding and a vectorial diagram of the phase voltagecomponents induced in the different coils of one phase of the winding;

FIG. 3 is a vector diagram of the voltages induced in the aforementionedsegments when connected according to the prior art;

FIG. 4 is a corresponding schematic diagram of the prior art showing theseries connection of winding segments into pairs which comprise thecircuits ofa phase winding;

FIG. 5 is a schematic diagram showing the connection of winding segmentstaught by the present invention; and

FIG. 6 is a vector diagram of the voltages induced in the segments whenconnected according to the teaching of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of thedrawings, there is illustrated a developed length of a stator core 10 ofa polyphase generator, and poles l1 and 12 of a rotor, such as is foundin a typical AC generator. For purposes of illustration, the generatorwill be considered to be of the two-pole, three phase type, each phaseconsisting of three individual circuits. The windings are separated intofirst and second phase belts A and A which are displaced 180 withrespect to one another within the stator. Each phase belt consists ofthree segments, each of which is constituted by a plurality ofseries-connected coils. The coils of first, second and third segments offirst phase belt A are denoted l, 2 and 3, respectively. Correspondingsegments of second phase belt A are denoted 1, 2 and 3+, respectively.To equalize the phase of net voltages of circuits comprising pairs ofsaid segments, it will be noted that individual coils of the windingsegments are distributed in a first sequence in the first phase belt.While it is recognized that different sequences may be selected, forpurposes of illustration sequences 123123123123 and 32'13213'21321 areused for phase belts A and A, respectively.

Referring now to FIG. 2, it will be seen that the centerlines of thegroups of coils constituting the winding segments are not colinear. Thecoils of the various segments cyclically alternate in succeeding statorcore slots, the centerline of each segment being thus displaced fromthat of the other segments of the same phase belt by the distanceseparating corresponding coils of the segments. 1n the illustratedembodiment, for example, the centerline of segment 3 is displaced onecore slot from that of segment 2, and two core slots from that ofsegment 1. The phasors representing voltages induced in these segments,labeled V V and V and lying along the centerline of each segment, aretherefore similarly displaced. Since there are 72 core slots in theillustrated embodiment, the angle between adjacent phases is that of onecore slot, or 5.

As indicated in FIG. 2, the armature windings of a threephase generatorcomprise three positive phase belts (respectively designated A, B andC), and three negative phase belts (respectively designated A, B and C)arranged in sequence about the inner diameter of stator core 10. Eachphase belt is identical in that it is constituted by three circuitsegments, each segment comprising a plurality of series-connected coils,and the coil sides of the segments being arranged in a suitable sequencein the core slots.

DISCUSSION OF THE PRIOR ART FIG. 3 shows a vector representation of thesegment voltages generated according to a prior art arrangement of theaforementioned Harrington US. Pat. No. 3,152,273. It will be seen thatall such segment voltages are of the same magnitude. While voltagesgenerated in winding segments 1 and 3 of phase belt A are out of phasewith respect to the voltages generated in corresponding winding segmentsl'and 3 respectively, of phase belt A, the net vector sums are in phasewith one another and with the voltages generated in winding segments 2and 2.

Referring now to FIG. 4, a simplified schematic diagram of the sixsegments constituting two phase belts of a single phase is shown. Aspointed out above, the segments in phase belt A are displaced 180 withinthe stator from those of phase belt A. Corresponding segments in eachphase belt are connected in series by means of connection rings 11, 22and 33 to form three circuits, each constituting one-third of a phase.For example, segment 1 of phase belt A is series-connected with segment1' of the phase belt A. Since the voltage being generated in phase beltA by an N pole is identical to the corresponding voltage generated inphase belt A by an S pole, the voltage in winding segments 2 and 2',which are located symmetrically about the centerlines of theirrespective phase belts, are in phase with each other and with theirresultant sum. The voltages generated in series-connected segments 1 andl are identical in magnitude but have equal but opposite phase angledisplacements from their resultant sum. The same is true forseries-connected segments 3 and 3. Therefore, the phase angle of theresultant voltages for all circuits is the same, and the magnitude ofthe resultant voltages for segments l-l' and 3-3' is very nearly equalto that for seriesconnected segments 2-2.

Circuits 1, 2 and 3 are constituted by connecting the proper segments inseries by means of connection rings 11, 22 and 33 respectively. Sincethe series-connected segments are located approximately opposite oneanother within the stator, it is thus necessary for the connection ringsto extend approximately one-half way about the periphery of that statorcore in order to connect the segments. Since there are three phases,each consisting of three parallel circuits, a total of nine connectionrings must be used. The only available space for these connection ringsis at the ends of the stator core, where space is at a premium. All coilconnections are also made at the stator core ends and, in the case ofmachines having fluid-cooled windings, provision must be made forrouting the cooling fluid from one coil to the next, and for conductingthe fluid to and from the external heat exchanger. It will thus be seenthat the presence of the aforementioned nine connection rings in thisprior art winding arrangement causes the length of the generator statorto increase significantly, and complicates assembly of the windings.

SCHEMATIC AND VECTOR DIAGRAMS OF ONE PREFERRED EMBODIMENT FIG. 5 is aschematic diagram showing the winding arrangement of the subjectinvention. A pair of segments in each phase belt are series-connected byleads and 330, the remaining segment being connected in series with itsmate in the opposite phase belt by means of connection ring 22. Althoughconnections must still be made between segments 1 and 3, and 1 and 3,referring back to FIG. 1, it will be noted that since the segments arecomposed of windings which are distributed beneath the same pole theconnection between the segments need only be very short.

FIG. 6 is a vector diagram of the voltages generated in the varioussegments, with the vectors relocated to indicate the connection schemetaught by the subject invention. It will be seen that vectorsrepresenting voltages generated in winding segments 1 and 3 are nowadditive; similarly, vectors representative of voltages generated inwinding segments 1' and 3' are also additive. As was the case with theprior art circuit of FIG. 3, the vector sums of these voltages are inphase with one another and also in phase with the voltages generated insegments 2 and 2'. The circuit of the subject invent-ion thus providesan output which is electrically identical to that of the prior art,although the interconnection of winding segments is significantlydifferent. It will be understood by those skilled in the art seen thatthe circuit of the subject invention may be used with various windingpatterns wherein the sequence of the coils constituting the variouswinding segments is different from that shown in the present embodiment.Further, the advantages inherent in the prior art in the use of aplurality of paralled circuits for each phase of a polyphase generatorare still present, and are in no way diminished by the connectionconfiguration taught by the present invention.

While the embodiment described herein is considered to be the preferredembodiment of the subject invention, it will be understood that variousmodifications may be made therein, such as utilizing a differentsequence of placement of the windings beneath a given pole, or theseries connection of segments employing connections from segment endsopposite those depicted. It will also be understood that while theinvention has been described in an embodiment utilizing only a singlepair of poles, it can be employed with equal efficacy to machinesutilizing more than one pair of poles, by connecting the phase windingsections from each pole-pair, as herein described, or in series or inequal series-parallel combinations. It is intended that the appendedclaims cover such modifications as well as any others which may fallwithin the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. In a dynamoelectric machine having a polyphase armature winding, eachphase of said winding comprising a first and a second phase belt, thewinding segments constituting said first phase belt being distributed ina first sequence within a stator, and the winding segments constitutingsaid second phase belt being distributed in a stator in a secondsequence which is the inverse of said first sequence:

a. first conductor means for serially connecting pairs of windingsegments having generated therein voltages of substantially equalmagnitude, and located in common phase belts;

b. second conductor means for serially connecting a first windingsegment of a first phase belt and a second winding segment of a second,opposing phase belt, said winding segments having generated thereinvoltages of substantially equal phase and magnitude; and

0. third conductor means for connecting in parallel the circuitsconstituted by saidserially-connected winding segments of said first andsecond phase belts.

2. A polyphase generator winding according to claim 1 wherein said firstand said second phase belts each include a first, second and thirdwinding segment, said first and third winding segments of each phasebelt being connected in series, and said second winding segment of saidfirst phase belt being connected in series with said second windingsegment of said second phase belt.

3. A polyphase generator winding according to claim 2 wherein said thirdconductor means connects each circuit constituted by saidserially-connected winding segments of said first and second phase beltsin parallel whereby only one of said circuits has a connection betweensaid winding segments.

1. In a dynamoelectric machine having a polyphase armature winding, eachphase of said winding comprising a first and a second phase belt, thewinding segments constituting said first phase belt being distributed ina first sequence within a stator, and the winding segments constitutingsaid second phase belt being distributed in a stator in a secondsequence which is the inverse of said first sequence: a. first conductormeans for serially connecting pairs of winding segments having generatedtherein voltages of substantially equal magnitude, and located in commonphase belts; b. second conductor means for serially connecting a firstwinding segment of a first phase belt and a second winding segment of asecond, opposing phase belt, said winding segments having generatedtherein voltages of substantially equal phase and magnitude; and c.third conductor means for connecting in parallel the circuitsconstituted by said serially-connected winding segments of said firstand second phase belts.
 2. A polyphase generator winding according toclaim 1 wherein said first and said second phase belts each include afirst, second and third winding segment, said first and third windingsegments of each phase belt being connected in series, and said secondwinding segment of said first phase belt being connected in series withsaid second winding segment of said second phase belt.
 3. A polyphasegenerator winding according to claim 2 wherein said third conductormeans connects each circuit constituted by said serially-connectedwinding segments of said first and second phase belts in parallelwhereby only one of said circuits has a 180* connection between saidwinding segments.